The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
In typical systems, recession is created after lapping and pre-carbon etching processes. This creates a distance between the transducers and the disk surface. Thermal fly-height control (TFC) is a method of altering this distance between the transducers and the disk surface by heating the components of the reader/writer causing thermal expansion of the materials, which results in the reader/writer transducers protruding closer to the surface of the hard disk. The transducers are moved closer to the disk surface to enable proper reading and writing of the tracks.
In some systems, the magnetic head includes an Embedded Contact Sensor (ECS) which is embedded in a layer of alumina (the alumina provides electrical isolation for the ECS). The ECS allows for determination of the distance between the magnetic head and the rotating disk surface. The ECS typically is constructed of a resistive film which detects contact through a change in resistance. This design, however, has a limited ability to detect touch-down (contact between the magnetic head and the rotating disk) due to several factors, including: (1) the alumina may be recessed where the ECS is typically embedded; (2) the location of the ECS may not be a minimum clearance point between the magnetic head and the rotating disk; and (3) the ECS sensor may be subject to wear if it locally protrudes from the magnetic head (e.g., it is the minimum clearance point). Of course, there are other factors which limit the usefulness and/or effectiveness of a conventional ECS design as well, which will not be discussed here.
Therefore, there is a need to design an integrated touch-down pad and touch-down sensor to ensure more effective touch-down detection and increase reliability of touch-down detection, and improve longevity of the touch-down sensor.